/*
silverPDF is sponsored by Aleyant Systems (http://www.aleyant.com)

silverPDF is based on PdfSharp (http://www.pdfsharp.net) and iTextSharp (http://itextsharp.sourceforge.net)

Developers: Ai_boy (aka Oleksii Okhrymenko)

Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated documentation
files (the "Software"), to deal in the Software without
restriction, including without limitation the rights to use,
copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following
conditions:

The above information and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR SPONSORS
BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.

*/
#region PDFsharp - A .NET library for processing PDF
//
// Authors:
//   Stefan Lange (mailto:Stefan.Lange@pdfsharp.com)
//
// Copyright (c) 2005-2008 empira Software GmbH, Cologne (Germany)
//
// http://www.pdfsharp.com
// http://sourceforge.net/projects/pdfsharp
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
// DEALINGS IN THE SOFTWARE.
#endregion

// With this define each iref object gets a unique number (uid) to make them distinguishable in the debugger
#define UNIQUE_IREF

using System;
using System.Diagnostics;
using System.Collections;
using System.Text;
using System.IO;
using PdfSharp.Internal;
using PdfSharp.Pdf.IO;

namespace PdfSharp.Pdf.Advanced
{
  /// <summary>
  /// Represents an indirect reference to a PdfObject.
  /// </summary>
  [DebuggerDisplay("iref({ObjectNumber}, {GenerationNumber})")]
  public sealed class PdfReference : PdfItem
  {
    // About PdfReference 
    // 
    // * A PdfReference holds the either ObjectID or the PdfObject or both.
    // 
    // * Each PdfObject has a PdfReference if and only if it is an indirect object. Direct objects have
    //   no PdfReference, because they are embedded in a parent objects.
    //
    // * PdfReference objects are used to reference PdfObject instances. A value in a PDF dictionary
    //   or array that is a PdfReference represents an indirect reference. A value in a PDF dictionary or
    //   or array that is a PdfObject represents a direct (or embeddded) object.
    //
    // * When a PDF file is imported, the PdfXRefTable is filled with PdfReference objects keeping the
    //   ObjectsIDs and file positions (offsets) of all indirect objects.
    //
    // * Indirect objects can easily be renumbered because they do not rely on their ObjectsIDs.
    //
    // * During modification of a document the ObjectID of an indirect object has no meaning,
    //   except that they must be different in pairs.

    /// <summary>
    /// Initializes a new PdfReference instance for the specified indirect object.
    /// </summary>
    public PdfReference(PdfObject pdfObject)
    {
      Debug.Assert(pdfObject.Reference == null, "Must not create iref for an object that already has one.");
      this.value = pdfObject;
#if UNIQUE_IREF && DEBUG
      this.uid = ++PdfReference.counter;
#endif
    }

    /// <summary>
    /// Initializes a new PdfReference instance from the specified object identifier and file position.
    /// </summary>
    public PdfReference(PdfObjectID objectID, int position)
    {
      this.objectID = objectID;
      this.position = position;
#if UNIQUE_IREF && DEBUG
      this.uid = ++PdfReference.counter;
#endif
    }

    /// <summary>
    /// Writes the object in PDF iref table format.
    /// </summary>
    internal void WriteXRefEnty(PdfWriter writer)
    {
      // PDFsharp does not yet support PDF 1.5 object streams.

      // Each line must be exactly 20 bytes long, otherwise Acrobat repairs the file.
      string text = String.Format("{0:0000000000} {1:00000} n\n",
        this.position, this.objectID.GenerationNumber); // this.InUse ? 'n' : 'f');
      writer.WriteRaw(text);
    }

    /// <summary>
    /// Writes an indirect reference.
    /// </summary>
    internal override void WriteObject(PdfWriter writer)
    {
      writer.Write(this);
    }

    /// <summary>
    /// Gets or sets the object identifier.
    /// </summary>
    public PdfObjectID ObjectID
    {
      get { return this.objectID; }
      set
      {
        if (this.objectID != value)
        {
          this.objectID = value;
          if (this.Document != null)
          {
            //PdfXRefTable table = this.Document.xrefTable;
            //table.Remove(this);
            //this.objectID = value;
            //table.Add(this);
          }
        }
      }
    }
    PdfObjectID objectID;

    /// <summary>
    /// Gets the object number of the object identifier.
    /// </summary>
    public int ObjectNumber
    {
      get { return this.objectID.ObjectNumber; }
    }

    /// <summary>
    /// Gets the generation number of the object identifier.
    /// </summary>
    public int GenerationNumber
    {
      get { return this.objectID.GenerationNumber; }
    }

    /// <summary>
    /// Gets or sets the file position of the related PdfObject.
    /// </summary>
    public int Position
    {
      get { return this.position; }
      set { this.position = value; }
    }
    int position;  // I know it should be long, but I have never seen a 2GB PDF file.

    //public bool InUse
    //{
    //  get {return this.inUse;}
    //  set {this.inUse = value;}
    //}
    //bool inUse;

    /// <summary>
    /// Gets or sets the referenced PdfObject.
    /// </summary>
    public PdfObject Value
    {
      get { return this.value; }
      set
      {
        this.value = value;
        // value must never be null
        value.Reference = this;
      }
    }
    PdfObject value;

    /// <summary>
    /// Hack for dead objects.
    /// </summary>
    internal void SetObject(PdfObject value)
    {
      this.value = value;
    }

    /// <summary>
    /// Gets or sets the document this object belongs to.
    /// </summary>
    public PdfDocument Document
    {
      get { return this.document; }
      set { this.document = value; }
    }
    PdfDocument document;

    /// <summary>
    /// Gets a string representing the object identifier.
    /// </summary>
    public override string ToString()
    {
      return this.objectID.ToString() + " R";
    }

    internal static PdfReferenceComparer Comparer
    {
      get { return new PdfReferenceComparer(); }
    }

    /// <summary>
    /// Implements a comparer that compares PdfReference objects by their PdfObjectID.
    /// </summary>
    internal class PdfReferenceComparer : IComparer
    {
      public int Compare(object x, object y)
      {
        PdfReference l = x as PdfReference;
        PdfReference r = y as PdfReference;
        if (l != null)
        {
          if (r != null)
            return l.objectID.CompareTo(r.objectID);
          else
            return -1;
        }
        else if (r != null)
          return 1;
        else
          return 0;
      }
    }

#if UNIQUE_IREF && DEBUG
    static int counter = 0;
    int uid;
#endif
  }
}
